The following items under the cut should be considered HUGE IMMENSE SPOILERS for those who want to find the Easter Egg by themselves. Remember, if you click on the LJ-Cut, don't go complaining that you've been spoiled. You Have Been Warned, and all that.
For those who may not know: an Easter Egg, in the context of a game (among other media), a hidden feature or message in the game that's really hidden.
Firstly, you're going to either need to be significantly-levelled (50 is best), or have an invisibility/stealth power and be quick on your feet. This is because the place we're going has plenty of Bane Spiders (the higher ranks of which can see through stealth), and various more interesting varieties of Arachnos Drones (like missile launchers and kamikaze explosive), all around level 47 or so. The invis/stealth helps in reducing the aggro radius ever so slightly, which may well help.
With that, head to the tunnels under Grandville. If you don't know where those are (I didn't), your first destination is the Fab. This is the small(er) island to the north of Spider City and such, and you'll know it by the big huge industrial structure and supports, mostly built from ground level downwards. It's dirt-coloured, mind. Shouldn't be too hard to find.
Next, go look for the entrance to the tunnels, and enter it. Be careful of all the Bane Spiders wandering around. The tunnels themselves are almost free of enemies; in my time wandering around down there, I met three Arachnos Drones, and only them. One of them blew up at me, and only the anti-one-shot code saved me. If you keep moving quickly, you shouldn't have a problem.
The path from here is pretty straightforward, being that there's only one way to go, but if you'd like directions anyway: right down the slope, left at the turn, right at the turn, right again at the turn, left and go forward for quite a ways up a few slopes, left at the turn, right at the turn, go forward up a slope, and then left, stopping before the next right turn.
If you find yourself at the gates to the City Core or the Beach Access, then you've gone too far. In this case, go back into the tunnels, left at the turn, and then stop at the next turn.
So. You should find yourself looking at some machines. (Map and /loc here.) What about it, you ask? Well, have a look at the gap. Look inside the gap. Interesting, isn't it?
The passage will lead you to a hidden office. Along the way (and almost throughout the tour of the Easter Egg), you'll hear, faintly in the distance, maniacal laughter, whip-cracks, and screams of agony (all on the SFX channel; I kept my Music volume at mute the entire time). It's a good thing nobody's in there, since we're apparently trespassing.
Coming into the office, you'll be greeted with the usual skull-in-a-cage, and then several cubicles. Lots of interesting things to see, right? But first, let's turn around and check the whiteboard behind us, to see who hath wrought this madness. To the left of the whiteboard is a picture of... well, I have no clue, really. Maybe I need to get better textures.
Let's start with the right side of the office (the side with three cubicles). First, we have Mike Apolis (picture), who has a very clean and neon-lit cubicle. Next down the line, Nick Duguid (picture), who always makes sure to eat his Hero-Os. Last is Mark Damico (picture), who is not to be outdone.
On the other side, we have Ken Morse (picture), who seems to like Chinese takeout a lot (or whatever the heck that is). And we have Ryan Roth (picture), who has, er, gone down protesting.
And last but certainly not least, Kirk Young, who communicates entirely by means of flatulently singing "Moon River". ("Moon Riveee*fart*eer, wider th*flush*an a mile...")
Very clever and very cool. And I may never listen to that song in the same way again.